Certain natural gas streams contain diamondoid compounds. These diamondoid compounds are a family of volatile C10+ hydrocarbons with lattice-like structures. Some of these diamondoids form solids at warmer than ambient (greater than 100 .degree. F.) temperatures when they are condensed from natural gas streams. These diamondoids are present in trace quantities in the natural gas reservoirs themselves.
New sources of hydrocarbon gases are now being produced which contain significantly higher concentrations of diamondoids. Whereas in the past the amount of diamondoid compounds has typically been too small to cause operational problems such as plugging of production equipment, these new sources have experienced the problem of plugging the natural gas production equipment. Costly maintenance and repair time is required to remove the diamondoids. These diamondoid solids must be removed from the natural gas stream by appropriate means to maintain satisfactory production operations.
Although recent patents by Alexander et al. (U.S. Pat. Nos. 4,952,747; 4,952,748; 4,952,749; 4,982,049) have disclosed methods of removing some fractions of diamondoids from gas streams, the adamantane fraction of diamondoids in particular produced with the natural gas cannot be adequately absorbed by the methods disclosed in the Alexander patents for diamondoid removal (such as contacting the gas stream with a liquid solvent in which diamondoids are partially soluble, by injecting the solvent into producing wellheads and flowlines and subsequently removing the diamondoids by separating the gas from the diamondoid-laden solvent). Although diamondoid content is reduced, these methods do not remove a sufficient portion of the diamondoids to allow satisfactory operation of equipment without the concern of diamondoids plugging downstream equipment. In fact, additional processes such as silica gel absorbents as described in U.S. Pat. No. 4,952,748 may be required for further diamondoid removal to satisfactory levels.
With the current methods, a sufficient amount of diamondoids may be removed only if an extremely large amount of liquid solvent is mixed with the diamondoid-laden gas. Therefore, problems associated with residual amounts of the light diamondoids still remain and can occur when using the current methods in several instances such as the following: 1) diamondoid amounts absorbed by downstream glycol dehydration solvent (e.g. 0.06 lb/gal of glycol) would quickly load the glycol system charcoal filters. Frequent (weekly) filter change-out would be necessary to maintain the capability of removing diamondoids as well as other normal glycol degradation products in order to prevent glycol fouling and foaming problems; 2) flash gas recompression equipment, which returns low pressure gas from the glycol dehydration regeneration systems to the main gas flow would be handling gas streams with significant (up to 1500 lb/MSCF) diamondoid concentrations. Upon compression and cooling, diamondoids in this flash gas would precipitate and likely plug compressor discharge coolers and inlet scrubber mist extractors; and 3) diamondoids remaining in the dehydrated gas may precipitate in the produced gas pipeline, thereby potentially causing scaling and plugging problems. Therefore, there remains a need for a diamondoid removal process that can remove a sufficient amount of diamondoids from the natural gas, such that equipment problems caused by residual amounts of diamondoids are reduced, without the use of unusually large amounts of solvent.